Electronic devices such as servers are installed in a data center. As a method of cooling the electronic devices, there is a method using outside air. According to this method, the outside air is taken into the data center by rotating fans, and the electronic devices are cooled directly with the outside air, without the outside air being cooled by using a heat exchanger and the like. Thus, this method does not require electric power for the heat exchanger and the like, and is therefore able to contribute to energy saving in the whole of the data center.
However, when the outside air is directly used in the case where the temperature of the outside air is high as in summer, the electronic devices may be cooled insufficiently. Moreover, when an air conditioner having a cooling function is used as an auxiliary cooler in order to prevent the insufficient cooling, the power required for the air conditioning increases by an amount for the air conditioner, in some operating conditions of the air conditioner, and the energy saving in the data center cannot be realized.
Note that techniques relating to the present application are disclosed in Japanese Laid-open Patent Publication No. 2009-300058 and Japanese Laid-open Patent Publication No. 2010-156494.